output stage

hey..i have to design an audio amplifier with a gain of around 3600V/V (load is a 10W, 4ohm speaker and input is 5mV(p-p) i have designed two stages and cascaded them for this gain (attached)..nw i have to design the output stage using class AB type biasing it with Vbe multiplier (using tip31c and tip32c transistors)...i designed one bt the gain drops remarkably wen i cascade it..hw shud i bias it so that the gain does not drop??

thanx alot for ur help i simulated ur design and the output voltage still does drop to a very small value ...plus y have u used the 0.1ohm resistors (just so dat i cud explain to my teacher) cud v use larger ones?

thanx alot for ur help i simulated ur design and the output voltage still does drop to a very small value ...plus y have u used the 0.1ohm resistors (just so dat i cud explain to my teacher) cud v use larger ones?

Audioguru, you are reminded that not all AAC members are natives of an English-speaking country, nor are obliged to have an impeccable English language education.

AAC is an English speaking forum, but only to provide a common base of conversation between its members. Good use of the English language facilitates conversation, but is not absolutely required to participate in the forums.

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I simulated this circuit. And the voltage gain is equal to 90KV/V
So I need reduce the gain.

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i cant seem to understand the purpose of R3,C2,T3,R4,R8,Re2 and Re3... could you please explain that to me... and why isnt your output stage design working with my input stage cant we make a few changes in my design to make it work with yours?

i cant seem to understand the purpose of R3,C2,T3,R4,R8,Re2 and Re3... could you please explain that to me.

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R3 plus R4 apply negative feedback from the output to the base of T3 so that the output is at 0VDC. But then a high or low hFE of T3 changes it.
C2 filters the AC audio out of the negative feedback to keep the AC gain high.
T1 and T3 provide voltage gain (amplification).
R8 is the load for T5 and it can quickly turn off T7 when T5 turns off.
Re2 and Re3 reduce the differences in vbe and hfe of T7 and T8 so that they match better and so that their idle current is controlled.

why isnt your output stage design working with my input stage?

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The input stage here has a low output impedance from its T2 emitter-follower so it can drive the fairly low input impedance of T3.
Your input stage has a fairly high output impedance because it doesn't have an emitter-follower on its output and the low impedance of T3 loads it down and reduces its output level.

Thank you for turning off the weird "text speak used by little kids on their cell phones" and now you are speaking pretty good English.